# Development of Ultra-high-density Packaging for Implantable Neural Devices

> **NIH VA I21** · VETERANS HEALTH ADMINISTRATION · 2020 · —

## Abstract

A range of new applications of neural interfaces have developed in the past few decades.
Cochlear implants led to retinal implants, motor cortex recording prostheses, sensory prostheses,
and closed-loop sense and control devices that have yet to be developed. As these new systems
are invented, the number of recording or stimulation channels has increased, and our ambition
has outpaced certain areas of technology, specifically the hermetic packaging of implantable
devices.
For a device implanted into the body for many years, even decades, electronic circuits must be
protected from bodily fluids. Polymer coatings are sufficient to prevent liquid water from reaching
the circuits for many months, but water vapor can penetrate the loosely cross-linked chains and
condense on the electronics. Therefore, crystal structures are used in implanted devices to block
water vapor. These packages are often made of titanium and/or ceramic materials. Existing
hermetic packages are filled with helium before being sealed, and are tested for helium leakage.
This gives an easy translation to water vapor leakage into the device. This process allows every
single device to be tested, and a prediction made for its useful lifetime inside the body. However,
the technology to develop titanium or ceramic packages is limited in its ability to create high
density feedthroughs. My group has worked with vendors to create a feedthrough with a density
exceeding 300 channels per cm2, but the manufacturing and assembly process has been difficult.
Many devices would benefit from a density closer to 1000 channels per cm2, requiring the
development of new packaging technology.
We propose to use the same semiconductor technology used to create microchips to build the
package around the chip. This allows us to easily register to the chip pads to create connections,
reducing assembly complexity. We will add alternating layers of polymer and crystalline materials,
creating a hermetic barrier that is mechanically sound. However, such a device has no internal
space to accommodate helium for the traditional lifetime projection test. We have developed
procedures and circuits to measure very high impedances, and we propose to embed
interdigitated electrodes into the package layers, measuring the impedance to detect leakage.
We will measure initial water penetration to predict package lifetime, and we will also create a
system to monitor the impedance over the lifetime of a device, allowing for warnings as the device
nears the end of its lifetime.
We feel that these advances in high-density packaging and device testability will enable higher-
density versions of the VA peripheral nerve stimulator, as well as other existing implantable
devices, and inspire new devices and applications that will help our veteran population.

## Key facts

- **NIH application ID:** 9827987
- **Project number:** 5I21RX002890-02
- **Recipient organization:** VETERANS HEALTH ADMINISTRATION
- **Principal Investigator:** Shawn K. Kelly
- **Activity code:** I21 (R01, R21, SBIR, etc.)
- **Funding institute:** VA
- **Fiscal year:** 2020
- **Award amount:** —
- **Award type:** 5
- **Project period:** 2018-11-01 → 2020-10-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9827987

## Citation

> US National Institutes of Health, RePORTER application 9827987, Development of Ultra-high-density Packaging for Implantable Neural Devices (5I21RX002890-02). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/9827987. Licensed CC0.

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